Hard disk drive multiple contact disk clamp

ABSTRACT

A disk clamp for a hard disk drive, configured to clamp disk media to a spindle, includes multiple protrusions extending from a surface of a bottom side and configured to contact a disk medium at multiple contact positions in response to application of a clamping load. The protrusions may be annular protrusions circumscribing a disk clamp hub, where the height of an inner protrusion may be less than the height of an outer protrusion to inhibit coning of the top disk medium, and the protrusions may be positioned so that an equivalent contact radius corresponding to contact radii of the inner and outer annular protrusions is at a position halfway between the inner and outer diameters of the disk spacers to inhibit coning of the middle disk media.

FIELD OF EMBODIMENTS

Embodiments of the invention may relate generally to hard disk drives,and particularly to approaches to a disk clamp.

BACKGROUND

A hard disk drive (HDD) is a non-volatile storage device that is housedin a protective enclosure and stores digitally encoded data on one ormore circular disks having magnetic surfaces. When an HDD is inoperation, each magnetic-recording disk is rapidly rotated by a spindlesystem. Data is read from and written to a magnetic-recording disk usinga read-write head (or “transducer”) housed in a slider that ispositioned over a specific location of a disk by an actuator. Aread-write head makes use of magnetic fields to write data to and readdata from the surface of a magnetic-recording disk. A write head worksby using the current flowing through its coil to produce a magneticfield. Electrical pulses are sent to the write head, with differentpatterns of positive and negative currents. The current in the coil ofthe write head produces a localized magnetic field across the gapbetween the head and the magnetic-recording disk, which in turnmagnetizes a small area on the recording medium.

Increasing the storage capacity of hard disk drives (HDDs) is one of theon-going goals of HDD technology evolution. In one form, this goalmanifests in increasing the number of disks implemented in a given HDD.However, oftentimes maintaining a standard form factor is required, ascharacterized in part by the z-height of an HDD, which inherentlyprovides challenges with respect to fitting more disks into a given HDD.More particularly, customer specifications and/or common design andoperational constraints include operational shock (or “op-shock”)requirements, which generally relate to an HDD's operational toleranceof a mechanical shock event. As the number of disks in a given formfactor is increased, the disk stack clamping load (i.e., screw tensionloads) increases commensurately to adequately hold the disk stacktogether, especially in view of the op-shock requirements. Thus, itremains a challenge to increase the number of disks while maintaining astandard form factor, which consequently decreases the distance betweeneach disk of the disk stack, while also reliably meeting op-shockrequirements.

Any approaches that may be described in this section are approaches thatcould be pursued, but not necessarily approaches that have beenpreviously conceived or pursued. Therefore, unless otherwise indicated,it should not be assumed that any of the approaches described in thissection qualify as prior art merely by virtue of their inclusion in thissection.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments are illustrated by way of example, and not by way oflimitation, in the figures of the accompanying drawings and in whichlike reference numerals refer to similar elements and in which:

FIG. 1 is a plan view illustrating a hard disk drive, according to anembodiment;

FIG. 2 is a cross-sectional side view illustrating a hard disk driverecording disk stack;

FIG. 3 is a perspective view illustrating the axial deformation of therecording disks in a disk stack with a single contact disk clamp under amoderate screw load, according to an embodiment;

FIG. 4A is a bottom perspective view illustrating a multiple contactdisk clamp, according to an embodiment;

FIG. 4B is a bottom plan view illustrating the multiple contact diskclamp of FIG. 4A, according to an embodiment;

FIG. 4C is a cross-sectional view illustrating the multiple contact diskclamp of FIG. 4A, according to an embodiment;

FIG. 4D is a magnified cross-sectional view illustrating the multiplecontact points of the disk clamp of FIG. 4A, according to an embodiment;

FIG. 5 is a magnified cross-sectional view illustrating design geometryfor a multiple contact disk clamp, according to an embodiment;

FIG. 6 is a perspective view illustrating the axial deformation of therecording disks in a disk stack with a multiple contact disk clamp undera moderate screw load, according to an embodiment;

FIG. 7 is a flow diagram illustrating a method for coupling disk mediato a spindle, according to an embodiment;

FIG. 8 is a magnified cross-sectional view illustrating design geometryfor a multiple contact disk spindle motor hub flange, according to anembodiment;

FIG. 9 is a perspective view illustrating the axial deformation of therecording disks in a disk stack with a multiple contact disk clamp andspindle motor hub flange under a moderate screw load, according to anembodiment; and

FIG. 10 is a flow diagram illustrating a method for coupling disk mediato a spindle, according to an embodiment.

DETAILED DESCRIPTION

Generally, approaches to a disk clamp configured to inhibit disk coningare described. In the following description, for the purposes ofexplanation, numerous specific details are set forth in order to providea thorough understanding of the embodiments of the invention describedherein. It will be apparent, however, that the embodiments of theinvention described herein may be practiced without these specificdetails. In other instances, well-known structures and devices may beshown in block diagram form in order to avoid unnecessarily obscuringthe embodiments of the invention described herein.

INTRODUCTION Terminology

References herein to “an embodiment”, “one embodiment”, and the like,are intended to mean that the particular feature, structure, orcharacteristic being described is included in at least one embodiment ofthe invention. However, instances of such phrases do not necessarily allrefer to the same embodiment,

The term “substantially” will be understood to describe a feature thatis largely or nearly structured, configured, dimensioned, etc., but withwhich manufacturing tolerances and the like may in practice result in asituation in which the structure, configuration, dimension, etc. is notalways or necessarily precisely as stated. For example, describing astructure as “substantially vertical” would assign that term its plainmeaning, such that the sidewall is vertical for all practical purposesbut may not be precisely at 90 degrees throughout.

While terms such as “optimal”, “optimize”, “minimal”, “minimize”,“maximal”, “maximize”, and the like may not have certain valuesassociated therewith, if such terms are used herein the intent is thatone of ordinary skill in the art would understand such terms to includeaffecting a value, parameter, metric, and the like in a beneficialdirection consistent with the totality of this disclosure. For example,describing a value of something as “minimal” does not require that thevalue actually be equal to some theoretical minimum (e.g., zero), butshould be understood in a practical sense in that a corresponding goalwould be to move the value in a beneficial direction toward atheoretical minimum.

Context

Recall that as the number of disks in a given form factor is increasedto increase storage capacity, the disk stack clamping load increasescommensurately, especially in view of hard disk drive op-shockrequirements. Consequently, such a large clamping load produces asubstantial coning deformation in the disks which can adversely affectthe read and write process above an acceptable tolerance.

FIG. 2 is a cross-sectional side view illustrating a hard disk driverecording disk stack. Disk stack 200 comprises a plurality of disk media202 rotatably mounted on, secured to, coupled with, clamped to a diskspindle 204 (see also spindle 124 of FIG. 1 ), which is typically partof a spindle drive motor 205 (shown here in simplified form) comprisingthe spindle hub 208 and hub flange 209. Disk stack 200 further comprisesa plurality of disk spacers 203 interposed between adjacent disk mediaof the plurality of disk media 202. Depicted here is an examplecorresponding to a 2-inch high form factor hard disk drive (HDD)utilizing twenty (20) disk media 202. A single-contact disk clamp 206having a single contact point 206 a (or contact surface) is coupled tothe spindle 204 to apply a clamping force or load to the stack of diskmedia 202 and disk spacers 203 to secure the disk media 202 to thespindle hub 208 so that the disk media 202 and disk spacers 203 rotatewith the hub 208, whereby the disk clamp 206 is fastened to the spindle204 using a circular series of fasteners 207 (e.g., typically threadedscrews). The term “spindle” may refer generally to the rotating hub(e.g., hub 208), and everything affixed to rotate with the hub, such asthe disk clamp (e.g., disk clamp 206) and what it clamps (e.g., diskmedia 202 and disk spacers 203).

Similarly, a single-contact hub flange 209 having a single contact pointor contact surface, in conjunction with the disk clamp 206, applies theclamping force or load to the stack of disk media 202 and disk spacers203. Conventional designs typically hold a single line of annularcontact between the disk clamp 206 (or clamp hub) and the disk media202, and a single line of annular contact between the hub flange 209 andthe disk media 202. Hence, the disk media 202 at the top (top diskmedium 202 a) and at the bottom (bottom disk medium 202 b) of the diskpack 200 largely deform and cone away from the point of contact.

FIG. 3 is a perspective view illustrating the axial deformation of therecording disks in a disk stack with a single contact disk clamp under amoderate screw load, according to an embodiment. To maintain clarity,FIG. 3 is a depiction of just a sliver of the disk media 202 of diskstack 200 (e.g., a 30° sliver of the disk stack is depicted here, ratherthan the full 360° of the disk stack), showing how the disk media 202are likely to deform (e.g., also referred to “coning”) under a nominalor designated clamping load (i.e., screw tension loads) from thesingle-contact disk clamp 206. Note here how the top or clamp-facing,clamp-contacting disk medium 202 a deforms under the clamping load, byincreasingly deflecting upward from its inner diameter (ID) to its outerdiameter (OD), outboard of where the disk clamp 206 is in contact withthe disk medium 202 a. In this example 2-inch HDD design, the coning issignificantly worse than with a common 1-inch form factor HDD design, asthe clamping load needed to secure the additional disk media (e.g., from10 disks to 20 disks) is commensurate with the number of disks. Statedotherwise, the clamping load needed to secure 20 disk media is roughlytwice that needed to secure 10 disk media.

Multiple Contact Disk Clamp

A multiple contact disk clamp for a hard disk drive (HDD) includesmultiple contact points or surfaces (generally, “contacts”) between thedisk clamp and the top disk (e.g., an end disk), where an inner contactand an outer contact are radially offset and the inner contact isintentionally axially offset from the outer contact through anoptimization process. Such an optimization process is intended todetermine the optimum offset for the inner contact that keeps the topdisk relatively, substantially flat and also produces an equivalentcontact force of the two contacts substantially at the mid-radius (or“halfway”) of the spacers between the disks. Stated otherwise, theoptimized disk clamp of the described embodiments is intended to inhibitthe coning of the top disk with which the disk clamp is in contact,while also inhibiting the coning of the middle disks, i.e., the disksother than the end disks.

FIG. 4A is a bottom perspective view illustrating a multiple contactdisk clamp, FIG. 4B is a bottom plan view illustrating the multiplecontact disk clamp of FIG. 4A, FIG. 4C is a cross-sectional viewillustrating the multiple contact disk clamp of FIG. 4A, and FIG. 4D isa magnified cross-sectional view illustrating the multiple contactpoints of the disk clamp of FIG. 4A, all according to embodiments. Diskclamp 406 (or simply “clamp 406”) is configured to clamp disk media to aspindle, such as to clamp a disk stack such as disk media 202 (FIGS. 2-3) to a spindle of a drive motor such as spindle 204 (FIG. 2 ) of spindledrive motor 205 (FIG. 2 ).

Disk clamp 406 comprises a disk-facing side 406 d (or “bottom side”) anda cover-facing side 406 c (or “top side”), and multiple protrusions 406i, 406 o extending from a surface of the disk-facing side 406 d. Twoprotrusions 406 i (inner), 406 o (outer) are depicted here and foundsuitable for the described purpose, however, the number of protrusionsmay vary from implementation to implementation. The protrusions 406 i,406 o are configured to contact a disk medium such as end or top diskmedium 202 a (FIGS. 2-3 ) in response to application of a clamping load(or clamping force), such as by way of a series ofcircumferentially-spaced fasteners or screws (see, e.g., screw 207 ofFIG. 2 ), at multiple respective contact positions of the disk medium.According to an embodiment, each of the protrusions 406 i, 406 o isconfigured as an annular protrusion circumscribing a hub of the diskclamp 406, as depicted here, at a distance d apart from each other.

FIG. 5 is a magnified cross-sectional view illustrating design geometryfor a multiple contact disk clamp, according to an embodiment. Aspreviously introduced, disk clamp 406 is preferably designed to optimizethe axial offset (e.g., vertical, in context of the view of FIG. 5 ) forthe inner contact corresponding to inner protrusion 406 i relative tothe outer contact corresponding to outer protrusion 406 o, that keepsthe top disk medium 502 a substantially flat, or relatively flat in thecontext of comparing FIG. 6 (dual-contact disk clamp such as 406 ofFIGS. 4A-4D) with FIG. 3 (single-contact disk clamp such as 206 of FIG.2 ). Thus, the inner protrusion 406 i has a first height at itscenterline (“center height h_(i)”) and the outer protrusion 406 o has asecond center height h_(o), where the first center height h_(i) of innerprotrusion 406 i is less than the second center height h_(o) of outerprotrusion 406 o, with this axial offset referred to as offset h(h=h_(o)−h_(i)). The parameter h may vary from implementation toimplementation and indeed is expected to vary based on specific designconfigurations and, therefore, represents an optimization goal. Forexample, if the inner contact axial offset is zero (h=0 mm) then thecontact forces are entirely concentrated on the inner contact of innerprotrusion 406 i, as the outer protrusion 406 o loses contact with thedisk medium as the clamping load is applied by tightening the fasteners.By utilizing an offset h, the inner protrusion 406 i is initially not incontact with the disk medium 502 a as the clamping fasteners (see, e.g.,screw 207 of FIG. 2 ) are tightened and the contact forces are entirelyconcentrated on the outer contact of outer protrusion 406 o. Then as thefasteners are further tightened the disk clamp 406 begins to deform andthe inner protrusion 406 i is brought into contact with the disk medium502 a, at which point the effective contact force of the inner and outerprotrusions 406 i, 406 o begin to move from the outer diameter (OD)toward the inner diameter (ID) and continue to move inward as thefasteners are tightened further. Furthermore, as the inner contact axialoffset h increases and the effective contact force moves from the innercontact of inner protrusion 406 i toward the outer contact of outerprotrusion 406 o, the equivalent contact radius of the two contactslikewise moves from an inner radius toward an outer radius.

To inhibit coning of the top disk medium 502 a, as can be modeled and/ormeasured by the OD-to-ID axial difference, the contacts and thus theinner and outer protrusions 406 i, 406 o need to be a sufficientdistance apart, such as greater than 0.8 mm (millimeters) apart (i.e.,d>0.8 mm) for a non-limiting example and according to an embodiment.Effectively, the force concentration (or “effective force”) moves towardthe OD, or outboard, as h increases. However, as the radial distance dincreases, the contact forces show a lower sensitivity to the axialoffset h. With respect to the coning of the middle disks (the disksother than the end disks), an effective contact radius at a 50% offsetof the disk spacers 503 for a nominal torque load, i.e., at themid-radius or halfway point between the ID and OD of the spacers 503,has been found to produce a tolerable and optimum coning deformation ofthe middle disks. Thus, while the distance d between the inner and outerprotrusions 406 i, 406 o may vary from implementation to implementationand, therefore, d may represent an optimization goal, the effectiveradius of the force applied to the top disk medium 502 a via the innerand outer protrusions 406 i, 406 o, based on the respective contactradii of the inner and outer protrusions 406 i, 406 o, should preferablybe maintained at the spacer 503 mid-radius position for a nominal torqueload, according to an embodiment.

FIG. 6 is a perspective view illustrating the axial deformation of therecording disks in a disk stack with a multiple contact disk clamp undera moderate screw load, according to an embodiment. To maintain clarity,FIG. 6 is a depiction of just a sliver of the disk media 502 of diskstack (e.g., a 30° sliver of the disk stack is depicted here, ratherthan the full 360° of the disk stack), showing how the disk media 502are likely to deform under a nominal or designated clamping load (i.e.,screw tension loads) from the multiple-contact disk clamp 406 (FIGS.4A-5 ). Note here how the top or clamp-facing, clamp-contacting diskmedium 502 a minimally or negligibly deforms under the clamping loadoutward of where the disk clamp 406 is in contact with the disk medium502 a. In this example 2-inch HDD design, the coning is significantlybetter than that illustrated in FIG. 3 for a single-contact disk clamp.

Method for Coupling Disk Media to Spindle

FIG. 7 is a flow diagram illustrating a method for coupling disk mediato a spindle, according to an embodiment. For example, the method ofFIG. 7 can be used in conjunction with embodiments of disk clamp(s)illustrated and described in reference to FIGS. 4A-5 .

At block 702, position the disk media onto the spindle with disk spacersinterleaved therebetween. For example, disk media such as disk media 202(FIG. 2 ) are positioned onto the hub of a spindle such as spindle 204(FIG. 2 ), with disk spacers 203 (FIG. 2 ), 503 (FIG. 5 ) interleavedbetween each pair of adjacent disk media.

At block 704, position a disk clamp over a top disk medium, where thedisk clamp comprises multiple protrusions extending from a bottom side.For example, multiple contact disk clamp 406 (FIGS. 4A-5 ) having aninner protrusion 406 i and an outer protrusion 406 o is positioned ontothe spindle 204 over the group of disk media 202 and interleaved diskspacers 203, i.e., the disk stack, and in contact with the top diskmedium 502 a (FIG. 5 ).

At block 706, fasten the disk clamp to the spindle thereby forcing themultiple protrusions to contact the top disk medium to apply a clampingload at multiple respective contact positions of the top disk medium.For example, fasteners such as threaded screws 207 (FIG. 2 ) aretightened to fasten the disk clamp 406 to the spindle 204 therebyforcing the multiple protrusions 406 i, 406 o to contact the top diskmedium 502 a to apply a clamping load at multiple respective contactpositions of the top disk medium 502 a, where the contact positions (orcontact points, contact areas, contact surfaces) correspond to thecontact from protrusions 406 i, 406 o. Consequently the top disk medium502 a is minimally or negligibly deformed or coned under the clampingload outward of where the disk clamp 406 having multiple protrusions 406i, 406 o is in direct contact with the disk medium 502 a, such asillustrated in FIG. 6 .

Multiple Contact Disk Spindle Motor Hub Flange

A multiple contact disk spindle motor hub flange for a hard disk drive(HDD) includes multiple contact points or surfaces (generally,“contacts”) between the hub flange and the bottom disk (e.g., an enddisk), where an inner contact and an outer contact are radially offsetand the inner contact is intentionally axially offset from the outercontact through an optimization process. Such an optimization process isintended to determine the optimum offset for the inner contact thatkeeps the bottom disk relatively, substantially flat and also producesan equivalent contact force of the two contacts substantially at themid-radius (or “halfway”) of the spacers between the disks. Statedotherwise, the optimized disk spindle motor hub flange of the describedembodiments is intended to inhibit the coning of the bottom disk withwhich the hub flange is in contact, while also inhibiting the coning ofthe middle disks, i.e., the disks other than the end disks.

FIG. 8 is a magnified cross-sectional view illustrating design geometryfor a multiple contact disk spindle motor hub flange, according to anembodiment. The top portion of FIG. 8 is an angled side view of theassembly, with the bottom magnified portion of FIG. 8 being across-sectional side view. As previously introduced, hub flange 809 ispreferably designed to optimize the axial offset (e.g., vertical, incontext of the view of FIG. 8 ) for the inner contact corresponding toinner protrusion 809 i relative to the outer contact corresponding toouter protrusion 809 o, that keeps the bottom disk medium 802 bsubstantially flat, or relatively flat in the context of comparing FIG.9 (with dual-contact hub flange 809) with FIG. 3 (single-contact hubflange such as 209 of FIG. 2 ). Hub flange 809 comprises a disk-facingside 809 d (or “top side”) and a base-facing side 806 b (or “top side”),and multiple protrusions 809 i, 809 o extending from a surface of thedisk-facing side 809 d. Two protrusions 809 i (inner), 809 o (outer) aredepicted here and found suitable for the described purpose, however, thenumber of protrusions may vary from implementation to implementation.The protrusions 809 i, 809 o are configured to contact a disk mediumsuch as end or bottom disk medium 202 b, 802 b (FIGS. 2, 8 ) in responseto application of a clamping load (or clamping force), such as by way ofa series of circumferentially-spaced fasteners or screws (see, e.g.,screw 207 of FIG. 2 ), at multiple respective contact positions of thedisk medium. According to an embodiment, each of the protrusions 809 i,809 o is configured as an annular protrusion circumscribing the hub 808and/or hub flange 809 of the spindle.

The inner protrusion 809 i has a first height at its centerline (“centerheight h_(2i)”) and the outer protrusion 809 o has a second centerheight h_(2o), where the first center height h_(2i) of inner protrusion809 i is less than the second center height h₂, of outer protrusion 809o, with this axial offset referred to as offset h₂ (h₂=h_(2o)−h₂). Theparameter h₂ may vary from implementation to implementation and indeedis expected to vary based on specific design configurations and,therefore, represents an optimization goal. For example, if the innercontact axial offset is zero (h₂=0 mm) then the contact forces areentirely concentrated on the inner contact of inner protrusion 809 i, asthe outer protrusion 809 o loses contact with the disk medium as theclamping load is applied by tightening the fasteners. By utilizing anoffset h₂, the inner protrusion 809 i is initially not in contact withthe disk medium 802 a as the clamping fasteners (see, e.g., screw 207 ofFIG. 2 ) are tightened and the contact forces are entirely concentratedon the outer contact of outer protrusion 809 o. Then as the fastenersare further tightened the hub flange 809 begins to deform and the innerprotrusion 809 i is brought into contact with the bottom disk medium 802b, at which point the effective contact force of the inner and outerprotrusions 809 i, 809 o begin to move from the outer diameter (OD)toward the inner diameter (ID) and continue to move inward as thefasteners are tightened further. Furthermore, as the inner contact axialoffset h₂ increases and the effective contact force moves from the innercontact of inner protrusion 809 i toward the outer contact of outerprotrusion 809 o, the equivalent contact radius of the two contactslikewise moves from an inner radius toward an outer radius.

To inhibit coning of the bottom disk medium 802 b, as can be modeledand/or measured by the OD-to-ID axial difference, the contacts and thusthe inner and outer protrusions 809 i, 809 o need to be a sufficientdistance apart, such as greater than 0.8 mm (millimeters) apart (i.e.,d₂>0.8 mm) for a non-limiting example and according to an embodiment.Effectively, the force concentration (or “effective force”) moves towardthe OD, or outboard, as h₂ increases. However, as the radial distance d₂increases, the contact forces show a lower sensitivity to the axialoffset h₂. With respect to the coning of the middle disks (the disksother than the end disks), an effective contact radius at a 50% offsetof the disk spacers 503 for a nominal torque load, i.e., at themid-radius or halfway point between the ID and OD of the spacers 503,has been found to produce a tolerable and optimum coning deformation ofthe middle disks. Thus, while the distance d₂ between the inner andouter protrusions 809 i, 809 o may vary from implementation toimplementation and, therefore, d₂ may represent an optimization goal,the effective radius of the force applied to the bottom disk medium 802b via the inner and outer protrusions 809 i, 809 o, based on therespective contact radii of the inner and outer protrusions 809 i, 809o, should preferably be maintained at the spacer 503 mid-radius positionfor a nominal torque load, according to an embodiment.

FIG. 9 is a perspective view illustrating the axial deformation of therecording disks in a disk stack with a multiple contact disk clamp andspindle motor hub flange under a moderate screw load, according to anembodiment. To maintain clarity, FIG. 9 is a depiction of just a sliverof the disk media 902 of disk stack (e.g., a 30° sliver of the diskstack is depicted here, rather than the full 360° of the disk stack),showing how the disk media 902 are likely to deform under a nominal ordesignated clamping load (i.e., screw tension loads) from themultiple-contact disk clamp 406 (FIGS. 4A-5 ). Note here how the bottomor flange-facing, flange-contacting disk medium 802 b minimally ornegligibly deforms under the clamping load outward of where the hubflange 809 (FIG. 8 ) is in contact with the bottom disk medium 802 b. Inthis example 2-inch HDD design, the coning is significantly better thanthat illustrated in FIG. 3 for a single-contact disk clamp and asingle-contact hub flange, with respect to both the bottom disk medium802 b as well as the top disk medium 902 a.

Method for Coupling Disk Media to Spindle

FIG. 10 is a flow diagram illustrating a method for coupling disk mediato a spindle, according to an embodiment. For example, the method ofFIG. 10 can be used in conjunction with embodiments of disk spindle hubflange(s) illustrated and described in reference to FIG. 8 , and isdescribed in reference to FIGS. 8-9 .

At block 1002, position a bottom disk medium onto a spindle hub and incontact with a hub flange extending radially from the hub, where the hubflange includes multiple protrusions extending from a top side. Forexample, a disk medium such as disk media 802 b (FIG. 8 ) is positionedonto the hub of a spindle such as hub 808 (FIG. 8 ).

At block 1004, position middle disk media over the bottom disk mediumonto the spindle hub with disk spacers interleaved between adjacent diskmedia. For example, middle disk media such as disk media 902 (FIG. 9 )other than the top and bottom (end) disks 902 a, 802 b, are positionedonto the hub 808 over the bottom disk media 802 b, with disk spacers 503(FIG. 8 ) interleaved between each pair of adjacent disk media.

At block 1006, position a top disk medium over the middle disk mediaonto the spindle hub. For example, a disk medium such as disk media 902a (FIG. 9 ) is positioned onto the hub 808.

At block 1008, position a disk clamp over the top disk medium, where thedisk clamp comprises multiple protrusions extending from a bottom side.For example, multiple contact disk clamp 406 (FIGS. 4A-5 ) having aninner protrusion 406 i and an outer protrusion 406 o is positioned ontothe hub 808 over the group of disk media 902 (including top disk medium902 a and bottom disk medium 802 b) and interleaved disk spacers 503(i.e., the disk stack) and in contact with the top disk medium 902 a.

At block 1010, fasten the disk clamp to the spindle thereby forcing themultiple protrusions of the disk clamp to contact the top disk medium atmultiple respective contact positions of the top disk medium and forcingthe multiple protrusions of the hub flange to contact the bottom diskmedium at multiple respective contact positions of the bottom diskmedium. For example, fasteners such as threaded screws 207 (FIG. 2 ) aretightened to fasten the disk clamp 406 to the spindle 204 therebyforcing the multiple protrusions 406 i, 406 o of disk clamp 406 tocontact the top disk medium 902 a at multiple respective contactpositions of the top disk medium 902 a, where the contact positions (orcontact points, contact areas, contact surfaces) correspond to thecontact from protrusions 406 i, 406 o, and thereby also forcing themultiple protrusions 809 i, 809 o of hub flange 809 to contact thebottom disk medium 802 b at multiple respective contact positions of thebottom disk medium 802 b, where the contact positions (or contactpoints, contact areas, contact surfaces) correspond to the contact fromprotrusions 809 i, 809 o. Consequently the top disk medium 902 a and thebottom disk medium 802 b are minimally or negligibly deformed or conedunder the clamping load outward of where the disk clamp 406 havingmultiple protrusions 406 i, 406 o is in direct contact with the top diskmedium 902 a and outward of where the hub flange 809 having multipleprotrusions 809 i, 809 o is in direct contact with the bottom diskmedium 802 b, such as illustrated in FIG. 9 .

Physical Description of an Illustrative Operating Context

Embodiments may be used in the context of a digital data storage device(DSD) such as a hard disk drive (HDD). Thus, in accordance with anembodiment, a plan view illustrating a conventional HDD 100 is shown inFIG. 1 to aid in describing how a conventional HDD typically operates.

FIG. 1 illustrates the functional arrangement of components of the HDD100 including a slider 110 b that includes a magnetic read-write head110 a. Collectively, slider 110 b and head 110 a may be referred to as ahead slider. The HDD 100 includes at least one head gimbal assembly(HGA) 110 including the head slider, a lead suspension 110 c attached tothe head slider typically via a flexure, and a load beam 110 d attachedto the lead suspension 110 c. The HDD 100 also includes at least onerecording medium 120 rotatably mounted on a spindle 124 and a drivemotor (not visible) attached to the spindle 124 for rotating the medium120. The read-write head 110 a, which may also be referred to as atransducer, includes a write element and a read element for respectivelywriting and reading information stored on the medium 120 of the HDD 100.The medium 120 or a plurality of disk media may be affixed to thespindle 124 with a disk clamp 128.

The HDD 100 further includes an arm 132 attached to the HGA 110, acarriage 134, a voice-coil motor (VCM) that includes an armature 136including a voice coil 140 attached to the carriage 134 and a stator 144including a voice-coil magnet (not visible). The armature 136 of the VCMis attached to the carriage 134 and is configured to move the arm 132and the HGA 110 to access portions of the medium 120, all collectivelymounted on a pivot shaft 148 with an interposed pivot bearing assembly152. In the case of an HDD having multiple disks, the carriage 134 maybe referred to as an “E-block,” or comb, because the carriage isarranged to carry a ganged array of arms that gives it the appearance ofa comb.

An assembly comprising a head gimbal assembly (e.g., HGA 110) includinga flexure to which the head slider is coupled, an actuator arm (e.g.,arm 132) and/or load beam to which the flexure is coupled, and anactuator (e.g., the VCM) to which the actuator arm is coupled, may becollectively referred to as a head-stack assembly (HSA). An HSA may,however, include more or fewer components than those described. Forexample, an HSA may refer to an assembly that further includeselectrical interconnection components. Generally, an HSA is the assemblyconfigured to move the head slider to access portions of the medium 120for read and write operations.

With further reference to FIG. 1 , electrical signals (e.g., current tothe voice coil 140 of the VCM) comprising a write signal to and a readsignal from the head 110 a, are transmitted by a flexible cable assembly(FCA) 156 (or “flex cable”, or “flexible printed circuit” (FPC)).Interconnection between the flex cable 156 and the head 110 a mayinclude an arm-electronics (AE) module 160, which may have an on-boardpre-amplifier for the read signal, as well as other read-channel andwrite-channel electronic components. The AE module 160 may be attachedto the carriage 134 as shown. The flex cable 156 may be coupled to anelectrical-connector block 164, which provides electrical communication,in some configurations, through an electrical feed-through provided byan HDD housing 168. The HDD housing 168 (or “enclosure base” or“baseplate” or simply “base”), in conjunction with an HDD cover,provides a semi-sealed (or hermetically sealed, in some configurations)protective enclosure for the information storage components of the HDD100.

Other electronic components, including a disk controller and servoelectronics including a digital-signal processor (DSP), provideelectrical signals to the drive motor, the voice coil 140 of the VCM andthe head 110 a of the HGA 110. The electrical signal provided to thedrive motor enables the drive motor to spin providing a torque to thespindle 124 which is in turn transmitted to the medium 120 that isaffixed to the spindle 124. As a result, the medium 120 spins in adirection 172. The spinning medium 120 creates a cushion of air thatacts as an air-bearing on which the air-bearing surface (ABS) of theslider 110 b rides so that the slider 110 b flies above the surface ofthe medium 120 without making contact with a thin magnetic-recordinglayer in which information is recorded. Similarly in an HDD in which alighter-than-air gas is utilized, such as helium for a non-limitingexample, the spinning medium 120 creates a cushion of gas that acts as agas or fluid bearing on which the slider 110 b rides.

The electrical signal provided to the voice coil 140 of the VCM enablesthe head 110 a of the HGA 110 to access a track 176 on which informationis recorded. Thus, the armature 136 of the VCM swings through an arc180, which enables the head 110 a of the HGA 110 to access varioustracks on the medium 120. Information is stored on the medium 120 in aplurality of radially nested tracks arranged in sectors on the medium120, such as sector 184. Correspondingly, each track is composed of aplurality of sectored track portions (or “track sector”) such assectored track portion 188. Each sectored track portion 188 may includerecorded information, and a header containing error correction codeinformation and a servo-burst-signal pattern, such as anABCD-servo-burst-signal pattern, which is information that identifiesthe track 176. In accessing the track 176, the read element of the head110 a of the HGA 110 reads the servo-burst-signal pattern, whichprovides a position-error-signal (PES) to the servo electronics, whichcontrols the electrical signal provided to the voice coil 140 of theVCM, thereby enabling the head 110 a to follow the track 176. Uponfinding the track 176 and identifying a particular sectored trackportion 188, the head 110 a either reads information from the track 176or writes information to the track 176 depending on instructionsreceived by the disk controller from an external agent, for example, amicroprocessor of a computer system.

An HDD's electronic architecture comprises numerous electroniccomponents for performing their respective functions for operation of anHDD, such as a hard disk controller (“HDC”), an interface controller, anarm electronics module, a data channel, a motor driver, a servoprocessor, buffer memory, etc. Two or more of such components may becombined on a single integrated circuit board referred to as a “systemon a chip” (“SOC”). Several, if not all, of such electronic componentsare typically arranged on a printed circuit board that is coupled to thebottom side of an HDD, such as to HDD housing 168.

References herein to a hard disk drive, such as HDD 100 illustrated anddescribed in reference to FIG. 1 , may encompass an information storagedevice that is at times referred to as a “hybrid drive”. A hybrid driverefers generally to a storage device having functionality of both atraditional HDD (see, e.g., HDD 100) combined with solid-state storagedevice (SSD) using non-volatile memory, such as flash or othersolid-state (e.g., integrated circuits) memory, which is electricallyerasable and programmable. As operation, management and control of thedifferent types of storage media typically differ, the solid-stateportion of a hybrid drive may include its own corresponding controllerfunctionality, which may be integrated into a single controller alongwith the HDD functionality. A hybrid drive may be architected andconfigured to operate and to utilize the solid-state portion in a numberof ways, such as, for non-limiting examples, by using the solid-statememory as cache memory, for storing frequently-accessed data, forstoring I/O intensive data, and the like. Further, a hybrid drive may bearchitected and configured essentially as two storage devices in asingle enclosure, i.e., a traditional HDD and an SSD, with either one ormultiple interfaces for host connection.

Extensions and Alternatives

In the foregoing description, embodiments of the invention have beendescribed with reference to numerous specific details that may vary fromimplementation to implementation. Therefore, various modifications andchanges may be made thereto without departing from the broader spiritand scope of the embodiments. Thus, the sole and exclusive indicator ofwhat is the invention, and is intended by the applicants to be theinvention, is the set of claims that issue from this application, in thespecific form in which such claims issue, including any subsequentcorrection. Any definitions expressly set forth herein for termscontained in such claims shall govern the meaning of such terms as usedin the claims. Hence, no limitation, element, property, feature,advantage or attribute that is not expressly recited in a claim shouldlimit the scope of such claim in any way. The specification and drawingsare, accordingly, to be regarded in an illustrative rather than arestrictive sense.

In addition, in this description certain process steps may be set forthin a particular order, and alphabetic and alphanumeric labels may beused to identify certain steps. Unless specifically stated in thedescription, embodiments are not necessarily limited to any particularorder of carrying out such steps. In particular, the labels are usedmerely for convenient identification of steps, and are not intended tospecify or require a particular order of carrying out such steps.

What is claimed is:
 1. A hard disk drive (HDD) comprising: a pluralityof disk media rotatably mounted on a spindle hub; a plurality of diskspacers each interposed between adjacent disk media of the plurality ofdisk media; a disk clamp coupled to the spindle and applying a clampingforce to the disk media and the disk spacers to secure the disk media tothe spindle hub, the disk clamp comprising: a disk-facing side and acover-facing side, and multiple protrusions extending from a surface ofthe disk-facing side and in contact with a disk medium of the pluralityof disk media, thereby applying the clamping force at multiplerespective contact locations on the disk medium; a plurality of headsliders each housing a read-write transducer configured to read from andto write to a respective disk medium; and an actuator configured formoving the head sliders to access portions of the disk media.
 2. The HDDof claim 1, wherein the multiple protrusions consist of two protrusions.3. The HDD of claim 1, wherein each of the multiple protrusionscomprises an annular protrusion circumscribing a hub of the disk clamp.4. The HDD of claim 3, wherein: the multiple protrusions consist of aninner annular protrusion having a first center height and an outerannular protrusion having a second center height; and the first centerheight is less than the second center height.
 5. The HDD of claim 3,wherein: the multiple protrusions consist of an inner annular protrusionand an outer annular protrusion; and the inner and outer annularprotrusions are positioned so that an equivalent contact radiuscorresponding to contact radii of the inner and outer annularprotrusions is at a position substantially halfway between an innerdiameter and an outer diameter of the disk spacers to inhibit coning ofthe middle disk media other than the disk medium.
 6. The HDD of claim 3,wherein: the multiple protrusions consist of an inner annular protrusionhaving a first center height and an outer annular protrusion having asecond center height; the first center height is less than the secondcenter height; and the inner and outer annular protrusions arepositioned so that an equivalent contact radius corresponding to contactradii of the inner and outer annular protrusions is at a positionsubstantially halfway between an inner diameter and an outer diameter ofthe disk spacers to inhibit coning of the middle disk media other thanthe disk medium.
 7. The HDD of claim 6, wherein: a distance between thecontact radii of the inner and outer annular protrusions is greater than0.8 millimeters to inhibit coning of the disk medium.
 8. A disk clamppart for a hard disk drive, the disk clamp configured to clamp diskmedia to a spindle, the disk clamp comprising: a bottom side and a topside, and multiple protrusions extending from a surface of the bottomside and configured to contact a disk medium at multiple respectivecontact positions of the disk medium in response to application of aclamping load.
 9. The disk clamp of claim 8, wherein the multipleprotrusions consist of two protrusions.
 10. The disk clamp of claim 8,wherein each of the multiple protrusions comprises an annular protrusioncircumscribing a hub of the disk clamp.
 11. The disk clamp of claim 10,wherein: the multiple protrusions consist of an inner annular protrusionhaving a first center height and an outer annular protrusion having asecond center height; and the first center height is less than thesecond center height.
 12. The disk clamp of claim 10, wherein: themultiple protrusions consist of an inner annular protrusion and an outerannular protrusion; and the inner and outer annular protrusions arepositioned so that an equivalent contact radius corresponding to contactradii of the inner and outer annular protrusions is at a positionsubstantially halfway between an inner diameter and an outer diameter ofassociated hard disk drive disk spacers.
 13. The disk clamp of claim 10,wherein: the multiple protrusions consist of an inner annular protrusionhaving a first center height and an outer annular protrusion having asecond center height; the first center height is less than the secondcenter height; and the inner and outer annular protrusions arepositioned so that an equivalent contact radius corresponding to contactradii of the inner and outer annular protrusions is at a positionsubstantially halfway between an inner diameter and an outer diameter ofassociated hard disk drive disk spacers.
 14. The disk clamp of claim 13,wherein: a distance between the contact radii of the inner and outerannular protrusions is greater than 0.8 millimeters to inhibit coning ofa mating recording disk.
 15. A method for coupling disk media to aspindle, the method comprising: positioning the disk media onto thespindle with disk spacers interleaved therebetween; positioning a diskclamp over a top disk medium, wherein the disk clamp comprises multipleprotrusions extending from a bottom side; and fastening the disk clampto the spindle thereby forcing the multiple protrusions to contact thetop disk medium to apply a clamping load at multiple respective contactpositions of the top disk medium.
 16. The method of claim 15, whereineach of the multiple protrusions comprises an annular protrusioncircumscribing a hub of the disk clamp.
 17. The method of claim 16,wherein: the multiple protrusions consist of an inner annular protrusionhaving a first center height and an outer annular protrusion having asecond center height; and the first center height is less than thesecond center height.
 18. The method of claim 16, wherein: the multipleprotrusions consist of an inner annular protrusion and an outer annularprotrusion; and the inner and outer annular protrusions are positionedso that an equivalent contact radius corresponding to contact radii ofthe inner and outer annular protrusions is at a position substantiallyhalfway between an inner diameter and an outer diameter of the diskspacers to inhibit coning of the middle disk media other than the diskmedium.
 19. The method of claim 16, wherein: the multiple protrusionsconsist of an inner annular protrusion having a first center height andan outer annular protrusion having a second center height; the firstcenter height is less than the second center height; and the inner andouter annular protrusions are positioned so that an equivalent contactradius corresponding to contact radii of the inner and outer annularprotrusions is at a position substantially halfway between an innerdiameter and an outer diameter of the disk spacers to inhibit coning ofthe middle disk media other than the disk medium.